316 J. DEBY ON THE STRUCTURE OF THE DIATOM VALVE. 



\ 



VTe next come to the researches of Messrs. Prinz and Van 

 Ermengem,* who studied in particular the fossil Diatoms from 

 the Cement Stone of Jutland and the London Clay. These 

 observers being experienced microscopists, but unfortunately not 

 special students of the Diatom acea?, omitted to compare the fossil 

 with the recent analogous forms, and were thus led to generalize 

 upon insufficient data when they stated that the Diatom valve is a 

 sieve-like organism. These really conscientious observers would, 

 I feel confident, have come to other conclusions had they had an 

 opportunity of examining some of the typical slides of recent 

 Diatoms in my possession. 



The most elaborate of recent researches on the Diatom valve 

 are those published and copiously illustrated by Dr. J. H. L. 

 Flogel,f in which the results coincide in almost every point with 

 those previously arrived at by Otto M tiller. 



During the same year Mr. J. D. Cox J undertook a careful 

 study of the Diatom valve and its fragments. I cannot, however, 

 fully endorse all his conclusions, but give them here in his own 

 words : — 



" We have thus been led to the conclusion that the Triceratium 

 is formed of two laminae connected by a hexagonal network, of 

 which the areolae are about as deep as the diameter of the 

 hexagons ;§ that the inner of these laminae is finely dotted with 

 lines of punctae radiant from the centre of the triangle ; and that 

 the outer lamina is very thin over the centre of each hex agon, to which 

 it is firmly connected by the walls of the areola?, which are thickened 

 so as to give a hemispherical interior form to the upper end of each." 



Further on || Mr. Cox adds : — 



" I have received from Mr. Thomas Christian, of Richmond, 

 Va., a slide containing a valve of Triceratium Favus, which, whilst 

 he was endeavouring to pick it up, split into two films, the inner 

 with its markings of dots in radial lines wholly separating from 

 the outer, which had deep hexagonal cells closed with the exterior 

 film, with markings or ' eye spots.' The inner film has also the 

 outline of the hexagons upon it, being the mark of the attachment 



* " Amer. Soc. Belz. Micr.," 1884 and 1885. 

 t " Jourl. Roy. Micr. Soc," 1884, Vol. iv, p. 665. 

 I " Amer. Jourl. of Micr.," 1884, Vol. iv., p. 837 ; Vol. v,p. 54. 

 § This assertion I cannot accept in a general way, as the depth is most 

 variable in different species of the same genus. — J. D. 

 || « Amer. Jl. of Micr.," p. 108. 



